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j0hnnyb0y84
07-23-2005, 12:01 PM
Hey guys, this is my first post... I generally like to come and just read, but I have a question that I need answered.

I run at a track about twice a week and perform HIIT training - I sprint for 15 seconds, rest for 23, and repeat 21 times (comes out to be 7 laps around the track). I understand that anything lasting under 30 seconds (correct me if I'm wrong) increases the recruitment of your fast twitch muscle fibers. However, since I'm peforming so many different cycles, will I still be utilizing my fast twitch (IIx and IIa), or would this be considered aerobic and be more geared towards the improvement of the Type I fibers?

Thanks in advance,

Johnny

PYROTAK
07-23-2005, 05:10 PM
HIIT is definetly anerobic. makes me wish i had an indoor track at my sad excuse for a university. i guess i could goto the outdoor track but its like 6-7 blocks from the gym.

d'Anconia
07-23-2005, 05:17 PM
I would think it'd help develop both fast and slow. The sprinting would obviously recruit the fast twitch fibers while the rest periods in between sprints would help with the slow twitch I believe.

So yeah your fast twitch fibers are being developed. BTW you are gnarly because your rest periods aren't that long. My rest periods are like at least a minute long but then again I'm not very well-conditioned for endurance.

PYROTAK
07-23-2005, 05:23 PM
my HIIT routine on the track is just sprint the 100 meters, and then jog the other 100m around the curve and thats a rep. and i usually do 8 reps of those before i get lazy.

clearly im not conditioned enough to do 21 reps. thats impressive haha.

Zygote
07-23-2005, 05:42 PM
It'd do both. Your slow twitch muscle fibres don't turn off when your doing exercise that stresses fast twitch. The way it works is initially your slow twitch muscle fibres activitate, if they can't do the job properly (your sprinting) then your type IIa and type IIb fibres are activated in that order. You'll never be using your fast twitch type IIb glycolytic (anerobic) without first using your slow twitch type I (oxidative) and type IIa fast (oxidative).

Also nothing is truly anerobic or aerobic, theres always a combination, just sometimes one predominates.

Zygote

d'Anconia
07-23-2005, 05:52 PM
my HIIT routine on the track is just sprint the 100 meters, and then jog the other 100m around the curve and thats a rep. and i usually do 8 reps of those before i get lazy.

clearly im not conditioned enough to do 21 reps. thats impressive haha.

Um yeah I walk the curves, and very slowly I might add. Supposedly how you do the rest period isn't that important but it's the sprinting that counts.

And Zygote pretty much hit the nail on the head.

PYROTAK
07-23-2005, 06:04 PM
hm. so walking is just as effective as jogging?

if that were true then id walk everytime. nothing is more painful than doing HIIT. all cardio is the bane of my existance.

d'Anconia
07-23-2005, 06:16 PM
hm. so walking is just as effective as jogging?

if that were true then id walk everytime. nothing is more painful than doing HIIT. all cardio is the bane of my existance.

Yeah well from what I understand you need to give your body time to replenish myoglobin stores before you go onto the next sprint.

dissipate
07-23-2005, 10:12 PM
--- snip ---
(12) Intense interval work also utilizes both the fast and slow twitch fibres, more fast twitch fibres because of the amount of work required of the body in such a short time period.
--- snip ---

http://www.wannabebig.com/article.php?articleid=165

jack_of_all
07-24-2005, 07:57 AM
Hey guys, this is my first post... I generally like to come and just read, but I have a question that I need answered.

I run at a track about twice a week and perform HIIT training - I sprint for 15 seconds, rest for 23, and repeat 21 times (comes out to be 7 laps around the track). I understand that anything lasting under 30 seconds (correct me if I'm wrong) increases the recruitment of your fast twitch muscle fibers. However, since I'm peforming so many different cycles, will I still be utilizing my fast twitch (IIx and IIa), or would this be considered aerobic and be more geared towards the improvement of the Type I fibers?

Thanks in advance,

Johnny

basically its like everyone said, but props to you man, thats some serious running you do.